The long term goal of this proposal is the development of a commercial point-of-care device capable of electronically sensing single circulating tumor cells (CTC) in the peripheral blood of a cancer patient. The viratrode is a nanotechnology platform that represents a significant technological advance. It contains an electrode-based biosensor and can provide an inexpensive format for point-of-care diagnosis with high sensitivity. The viratrode incorporates a bioaffinity layer consisting of a [unreadable]kelp forest[unreadable] of filamentous phage particles, in which each particle can display multiple ligands to a particular cancer cell surface marker. This format maximizes specificity and affinity, while minimizing biofouling. The viratrode incorporates a sensitive area detector capable of detecting single digit or lower nM concentrations of biomarkers. Our Technical Objectives focus on constructing viratrodes for detecting prostate cancer CTC[unreadable]s. Our target markers include PSA, PSMA, PSCA, and &#61537;v&#946;3 intergrins. The viratrodes will be optimized for the recognition and real-time electrical detection of prostate cancer cells that express the target markers in a biologically relevant fluid matrix.